NEET 2025 LECTURE NOTE - BIOLOGY [FIRST YEAR]
BOTANY
CHAPTER - 01
BIOLOGICAL CLASSIFICATION
There is a vast diversity in the living world so it is very difficult to study each and every organism. So it
is essential to group them in various categories based on their similarities and dissimilarities.
There are three main systems of classification - Artificial, Natural and Phylogenetic.
I. Artificial system of Classification
It is based on one or few morphological characters for grouping of organisms. Aristotle (350 BC)
divided plants into herbs, shrubs and trees. He also divided animals into two groups - with red blood
and without red blood.
II. Natural system of Classification
It is a system of classification which takes into consideration comparable study of a number of characters
so as to bring out natural similarities and dissimilarities and hence natural relationships among the
organisms. They include morphological characters, anatomical characters, cytological characters,
physiology, ontogeny or development, reproduction, cytochemistry and biochemistry, experimental
taxonomy etc. A natural system for classification of seed plants was proposed by Benthem and Hooker
(1862 - 1883)
III. Phylogenetic System of Classification
Classification based on evolutionary relationships of organisms is called phylogenetic system of
classification. First phylogenetic system was proposed by Engler and Prantl (1887 - 1999)
1. Two Kingdom Classification
Linnaeus introduce Two kingdom system of classification with Plantae and Animalia. Kingdoms was
developed that included all plants and animals respectively. This system was mainly based on presence
or absence of cell wall.
This system did not distinguish between :-
Eukaryotes and prokaryotes
Unicellular and multicellular organisms
Photosynthetic (green algae) and non-photosynthetic (fungi) organisms.
2. Five Kingdom Classification
Phylogenetic classification was developed by R.H. Whittaker (1969), an American taxonomist, divided
all the organisms into five kingdoms. He introduced kingdom fungi for multicellular heterotrophic
organisms with chitinised cell wall. Thus Whittaker’s five kingdoms are Monera, Protista, Fungi, Plantae
and Animalia.
3
, STUDY CENTRE
The main criteria for classification used by Whittaker include :
(i) Cell structure [Prokaryote / Eukaryote]
(ii) Body organisation [Unicellular / Multicellular]
(iii) Mode of nutrition [Autotroph / Heterotroph]
(iv) Reproduction
(v) Phylogenetic relationships
Advantages of Five Kingdom Classification
1. Separation of prokaryotes in to a separate kingdom - Monera
2. Separation of unicellular eukaryotes into kingdom Protista - eg. Chlamydomonas, Chlorella
3. Separation of fungi into a separate kingdom
4. It has tried to bring out phylogenetic relationships even amongst the primitive forms
5. Placement of Euglena in kingdom Protista
Drawbacks of Five Kingdom Classification
1. Monera and Protista contain both walled and wall - less organisms, photosynthetic and
non-photosynthetic organisms, unicellular, filamentous organisms.
2. Archaebacteria differ from other bacteria in structure, composition and physiology
3. Mycoplasmas are quite different from bacteria where they have been placed along with prokaryotes
4. Viruses have not been included in this system of classification.
4
, NEET 2025 LECTURE NOTE - BIOLOGY [FIRST YEAR]
KINGDOM MONERA
Monera is a kingdom of prokaryotes. It includes the most primitive forms of life. Monerans are adapted
to all types of habitats. They are found everywhere (cosmopolitan in distribution).
There are two major groups - of monerans.
Archaebacteria and Eubacteria
Archaebacteria
They are primitive or first formed bacteria (ancient bacteria). They live in extreme environmental conditions
like high acidity, high salt concentration etc. They survive in such conditions due to the specialised
composition of their cell wall. Their cell wall is made up of a polysaccharide called Pseudomurein.
Archaebacteria are of three major types - Thermoacidophiles, Halophiles, Methanogens.
1. Thermoacidophiles
They are temperature, acid loving bacteria.They are facultative anaerobes.
They often live in hot sulphur springs and can tolerate temperature as higher as 80oC and pH as low
as 2.
eg. Thermoplasma
2. Halophiles
They are salt loving bacteria. They are facultative anaerobes. They live in hyper saline lagoons, salt
lakes, dead sea etc.
eg. Halobacterium
3. Methonogens
They are methane producing bacteria.
They are obligate anaerobes. They are found in marshy habitat, swamps, sewage treatment plants
and in the gut of several ruminant animals like cows and buffaloes. So the dung of these animals
consist of these bacteria and can be used in biogas plant. eg. Methanobacterium, methanococcus
EUBACTERIA
They are true bacteria and cell wall is made up of peptidoglycan / Murein.
Eubacteria are classified into two :
1. Bacteria
2. Cyanobacteria
BACTERIA
Bacteria were first discovered by Leeuwenhoek.
Bacteria are of different size and shape. The average size of a bacterium is 3 5m .
Shapes of Bacteria
Bacteria are of 4 categories based on their shape. They are :
1. Coccus / cocci - spherical shaped
2. Bacillus / Bacilli - Rod shaped
5
BOTANY
CHAPTER - 01
BIOLOGICAL CLASSIFICATION
There is a vast diversity in the living world so it is very difficult to study each and every organism. So it
is essential to group them in various categories based on their similarities and dissimilarities.
There are three main systems of classification - Artificial, Natural and Phylogenetic.
I. Artificial system of Classification
It is based on one or few morphological characters for grouping of organisms. Aristotle (350 BC)
divided plants into herbs, shrubs and trees. He also divided animals into two groups - with red blood
and without red blood.
II. Natural system of Classification
It is a system of classification which takes into consideration comparable study of a number of characters
so as to bring out natural similarities and dissimilarities and hence natural relationships among the
organisms. They include morphological characters, anatomical characters, cytological characters,
physiology, ontogeny or development, reproduction, cytochemistry and biochemistry, experimental
taxonomy etc. A natural system for classification of seed plants was proposed by Benthem and Hooker
(1862 - 1883)
III. Phylogenetic System of Classification
Classification based on evolutionary relationships of organisms is called phylogenetic system of
classification. First phylogenetic system was proposed by Engler and Prantl (1887 - 1999)
1. Two Kingdom Classification
Linnaeus introduce Two kingdom system of classification with Plantae and Animalia. Kingdoms was
developed that included all plants and animals respectively. This system was mainly based on presence
or absence of cell wall.
This system did not distinguish between :-
Eukaryotes and prokaryotes
Unicellular and multicellular organisms
Photosynthetic (green algae) and non-photosynthetic (fungi) organisms.
2. Five Kingdom Classification
Phylogenetic classification was developed by R.H. Whittaker (1969), an American taxonomist, divided
all the organisms into five kingdoms. He introduced kingdom fungi for multicellular heterotrophic
organisms with chitinised cell wall. Thus Whittaker’s five kingdoms are Monera, Protista, Fungi, Plantae
and Animalia.
3
, STUDY CENTRE
The main criteria for classification used by Whittaker include :
(i) Cell structure [Prokaryote / Eukaryote]
(ii) Body organisation [Unicellular / Multicellular]
(iii) Mode of nutrition [Autotroph / Heterotroph]
(iv) Reproduction
(v) Phylogenetic relationships
Advantages of Five Kingdom Classification
1. Separation of prokaryotes in to a separate kingdom - Monera
2. Separation of unicellular eukaryotes into kingdom Protista - eg. Chlamydomonas, Chlorella
3. Separation of fungi into a separate kingdom
4. It has tried to bring out phylogenetic relationships even amongst the primitive forms
5. Placement of Euglena in kingdom Protista
Drawbacks of Five Kingdom Classification
1. Monera and Protista contain both walled and wall - less organisms, photosynthetic and
non-photosynthetic organisms, unicellular, filamentous organisms.
2. Archaebacteria differ from other bacteria in structure, composition and physiology
3. Mycoplasmas are quite different from bacteria where they have been placed along with prokaryotes
4. Viruses have not been included in this system of classification.
4
, NEET 2025 LECTURE NOTE - BIOLOGY [FIRST YEAR]
KINGDOM MONERA
Monera is a kingdom of prokaryotes. It includes the most primitive forms of life. Monerans are adapted
to all types of habitats. They are found everywhere (cosmopolitan in distribution).
There are two major groups - of monerans.
Archaebacteria and Eubacteria
Archaebacteria
They are primitive or first formed bacteria (ancient bacteria). They live in extreme environmental conditions
like high acidity, high salt concentration etc. They survive in such conditions due to the specialised
composition of their cell wall. Their cell wall is made up of a polysaccharide called Pseudomurein.
Archaebacteria are of three major types - Thermoacidophiles, Halophiles, Methanogens.
1. Thermoacidophiles
They are temperature, acid loving bacteria.They are facultative anaerobes.
They often live in hot sulphur springs and can tolerate temperature as higher as 80oC and pH as low
as 2.
eg. Thermoplasma
2. Halophiles
They are salt loving bacteria. They are facultative anaerobes. They live in hyper saline lagoons, salt
lakes, dead sea etc.
eg. Halobacterium
3. Methonogens
They are methane producing bacteria.
They are obligate anaerobes. They are found in marshy habitat, swamps, sewage treatment plants
and in the gut of several ruminant animals like cows and buffaloes. So the dung of these animals
consist of these bacteria and can be used in biogas plant. eg. Methanobacterium, methanococcus
EUBACTERIA
They are true bacteria and cell wall is made up of peptidoglycan / Murein.
Eubacteria are classified into two :
1. Bacteria
2. Cyanobacteria
BACTERIA
Bacteria were first discovered by Leeuwenhoek.
Bacteria are of different size and shape. The average size of a bacterium is 3 5m .
Shapes of Bacteria
Bacteria are of 4 categories based on their shape. They are :
1. Coccus / cocci - spherical shaped
2. Bacillus / Bacilli - Rod shaped
5
